In a vibratory machine or apparatus such as disclosed, for example, in Isaacson et al U.S. Pat. Nos. 3,173,664 and 3,643,384, an elongated tube or container having a U-shaped vertical cross-sectional configuration, is supported by a set of spring beams for oscillatory movement on an effective pivot axis. One or more sets of opposing electromagnets are supported below the container in opposing relation and on opposite sides of corresponding armatures which are rigidly connected to the container. When the electromagnets are energized, the container oscillates and produces orbital movement of a workload within the container. Usually, the work load consists of a predetermined weight of treating media and a batch of parts to be treated, for example, by a deburring, polishing or descaling operation.
One or more sets of opposing electromagnets are also used for vibrating or oscillating other forms of vibratory members such as a vibratory screen which operates to separate the parts from the media after the parts have been treated. In relatively small vibratory treating machines, only one set of opposing electromagnets may be required to produce the desired amplitude of vibration or oscillation of the container and work load. However, with larger machines, it is common to employ two or more sets of opposing electromagnets in order to obtain the desired amplitude of vibration with the larger and heavier work load of parts and media.
One important advantage of using electromagnets as provided by the fact that the power output of the electromagnets may be varied in infinitely small increments by varying the voltage of the electrical power supplied to the electromagnets. Thus the rate at which the parts are treated by the treating media and the intensity of the treatment, may be varied or precisely controlled by changing the voltage of the power supplied to the electromagnets. The change in voltage is commonly provided by means of a voltage regulator of the transformer type such as marketed under the trademark Variac.
The voltage regulator is connected to vary the voltage of the power supplied to all of the electromagnets in unison and is adjusted according to the type of treating media, the form of parts to be treated, the desired treating time, etc. It has been found that the voltage regulators which are used in connection with the larger vibratory machines, have become more and more expensive to construct or purchase and also have substantial mass or weight which significantly adds to the shipping cost of the vibratory machine and its electrical control system. Also large voltage regulators are subject to large energy losses when passing power through the large windings.